Method of forming ceramic products

Abstract

In a method of forming a refractory product wherein a mixture consisting of effective amounts of silica, alumina, aluminium nitride, and with or without silicon nitride, is provided, the mixture is surrounded with a protective medium and sintered at a temperature between 1200°-2000° C to form a single phase silicon aluminium oxynitride corresponding to the formula: Si 6 -z Al z N 8 -z O z , where z is greater than zero and less than or equal to 5, and when there is no silicon nitride in the mixture z is greater than or equal to 4 and less than or equal to 5, the improvement being the step of introducing into said mixture magnesium oxide in an amount of not more than 5% by weight to form a magnesium silicate glass and aid in densification of the ceramic material.

We claim: 
     
       1. In a method of forming a refractory product wherein a mixture consisting essentially of effective amounts of silica, alumina, aluminium nitride and silicon nitride are provided and the relative proportions of the silica, alumina, aluminium nitride and silicon nitride are such that there is formed, after surrounding with the protective medium and sintering at a temperature between 1200°-2000° C, a ceramic material consisting of a single phase silicon aluminium oxynitride corresponding to the formula:   Si.sub.6.sub.-z Al.sub.z N.sub.8.sub.-z O.sub.z     where z is greater than zero and less than or equal to 5, the improvement being the step of introducing into said mixture magnesium oxide in an amount of not more than 5% by weight to form a magnesium silicate glass and aid in densification of said ceramic material.   
     
     
       2. The method as claimed in claim 1 wherein at least part of the silica in said mixture is present as an impurity contained by the silicon nitride. 
     
     
       3. The method as claimed in claim 1, wherein at least part of the alumina in said mixture is contained as an impurity by the aluminium nitride. 
     
     
       4. The method as claimed in claim 1, wherein to provide alumina and silica in said mixture, a compound of alumina and silica is introduced into the starting materials used to produce the mixture. 
     
     
       5. In a method of forming a refractory product wherein a mixture consisting essentially of effective amounts of silica, alumina, and aluminium nitride are provided and the relative proportions of the silica, alumina and aluminium nitride are such that there is formed after surrounding with a protective medium and sintering at a temperature of between 1200°-2000° C, a ceramic material consisting of a single phase silicon aluminum oxynitride corresponding to the formula:   Si.sub.6.sub.-z Al.sub.z N.sub.8.sub.-z O.sub.z     where z is greater than or equal to 4 and less than or equal to 5, the improvement being the step of introducing into said mixture magnesium oxide in an amount of not more than 5% by weight to form a magnesium silicate glass and aid in densification of said ceramic material.   
     
     
       6. A method as claimed in claim 5, wherein at least part of the alumina present in said mixture is contained as an impurity by the aluminium nitride. 
     
     
       7. A method as claimed in claim 5, wherein to provide alumina and silica in said mixture, a compound of alumina and silica is introduced into the starting materials used to produce the mixture.